A spark plug for use in a combustion apparatus, such as an internal combustion engine, includes, for example, a center electrode extending in the direction of an axis, an insulator provided around the center electrode, a tubular metallic shell attached to the outside of the insulator, and a ground electrode whose proximal end portion is joined to a forward end portion of the metallic shell. The ground electrode is bent at its substantially intermediate portion in such a manner that its distal end portion faces a forward end portion of the center electrode, thereby forming a spark discharge gap between the forward end portion of the center electrode and a distal end portion of the ground electrode.
In recent years, there has been known a technique for improving erosion resistance by providing a noble metal tip at a forward end portion of the center electrode and/or a distal end portion of the ground electrode in a region adapted to form the spark discharge gap. In joining the noble metal tip to the ground electrode or the like, generally, laser welding by means of a YAG laser is used (refer to, for example, Patent Document 1). Specifically, a laser beam is intermittently radiated to the circumference or perimeter of the boundary between the noble metal tip and the ground electrode or the like, thereby joining the noble metal tip to the ground electrode or the like through formation of a fusion zone where components of the members are fused together.